A new class of scorpion toxin binding sites related to an A-type K+ channel:: pharmacological characterization and localization in rat brain

A new scorpion toxin (3751.8 Da) was isolated from the Buthus martensi venom, sequenced and chemically synthesized (sBmTX3), The A-type current of striatum neurons in culture completely disappeared when 1 muM sBmTX3 was applied (K-d = 54 nM), whereas the sustained K+ current was unaffected. I-125-sBmTX3 specifically bound to rat brain synaptosomes (maximum binding = 14 fmol mg(-1) of protein, K-d = 0.21 nM). A panel of toxins yet described as specific ligands for K+ channels were unable to compete with I-125-sBmTX3. A high density of I-125-sBmTX3 binding sites was found in the striatum, hippocampus, superior colliculus, and cerebellum in the adult rat brain. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.